Electrical amplifying device



July 26, 1938. R, WORRALL 2,124,609

ELECTRICAL AMPLIFYING DEVICEE Filed Dec. 11, 1935 2 Sheets-Sheet 1 F URTHEIP HMPL IFICH TIUN FURTHER flMPLIF/C/IT/ON INVENTOR Robe/'1 H W0 rra 7 A a aw ATTORNEY y 26, R. H. WORRALL 2,124,600

ELECTRICAL AMPLIFYING DEVICEE Filed Dec. 11, 1935 2 Sheets-Sheet 2 FURTHER AMPL/F/cATm/v INVENTOR ROZ EH H. Worrall ATTORNEY Patented July 26, 1938 .uni' rao STATES PATENT OFFICE 15 Claims. (01. 250-415)- a (Granted under the act of March 3, 1883, as

, amended Apr-i130, 1928; 370 0. G. 757) My invention relates broadly to electrical am-L. plifying devices and more particularly to methods of and means for varying a direct current potential derived from a circuit including a lightsensitive cell so that effectively alternating potentials may be impressed upon input terminals of an alternating current amplifying device.

One object of my invention is to provide a method and means for amplifying the output of a photo-electric cell circuit or other device that furnishes as an output a direct current of comparatively small magnitude, by using a straight alternating current amplifier.

Another object of my invention is the variation of D. C. potentials so as to make them effectively alternating in character.

Another object ofv my invention is to provide a method and means for creating a controllable alternating potential in a circuit which includes a photo-electric cell, wherein the cell itself forms no part of the oscillating circuit proper.

Another object of my invention is to provide a means for amplifying the energy controlled by a photo-electric cell directly through the medium of an alternating current audio frequency amplifier, instead of' the direct current amplifier customarily used, to furnish a reliable, simple, and inexpensive means for amplifying such energy.

Other objects and advantages of the invention will be apparent from the following description, taken in connection with the accompanying drawings, wherein the figures show several circuit diagrams that illustrate some of the preferred embodiments of my invention.

In Figs. 1 and 2. the magnitude of the impressed D. C. potential from a photoelectric cell circuit is caused to vary by means of a periodically varying capacity.

In Figs. 3, 4, and 5 an alternating E. M. F. from an external source is applied to vary the magniture of the impressed D. C. potential derived from a light-sensitive cell circuit.

In Figs. 6 and 7 the magnitude of the impressed D. C. potential from a light-sensitive source is varied by means of iron cored coils, connected in the circuit, and influenced by an externally applied fluctuating magnetic field.

A. light-sensitive cell which has radiation from a light source impressed upon its sensitive surface sets up a source of direct current E. M. F. This E. M. F., impressed directly upon the grid of a vacuum tube, can only be amplified by a D. C. amplifying circuit. By the methods disclosed in this invention, the said E. M. F. may be varied so as to actuate the input circuit of a vacuum tube, or other electrical device, in the same manner as though alternating potentials were impressed. I

In the figures, like numerals are used to designate like parts throughout.

Referring to Fig. 1, numeral l is an external light source capable of radiating luminous energy when lighted; 2 is a light-sensitive cell, either photo-electric or photo-galvanic, having an anode element 3 and a cathode element 4; 5 is a split, rotary, or other type of variable condenser connected across the anode and cathode of the lightsensitive cell; and 6 is an electron tube which may be of the three or more element type. For purposes of illustration, a. three elemenflheater type tube is shown, having a cathode i, aheater element 8, energized from any conventional power source, a control grid 9 and an anode it. A grid leak or biasing resistor ii is connected from control grid 9 to the negative side of a biasing battery l2, whose positive terminal is connected to the cathode i. From the junction of biasing resistor it with the negative terminal of biasing battery 82, one cathode branch connection leads directly to one side of condenser E, and on to anode 3 of cell 2. From the cathode i oi said cell a connection proceeds to the opposite side of condenser 5, on through a fixed condenser is, whose presence in the circuit is optional, to the opposite side of grid biasing resistor ii, and thence to control grid 9. The position of fixed condenser it need not be exactly as shown but may be between cathode ii and condenser E, or elsewhere as desired to produce like results. Another cathode branch connection ieads from cathode l, to the center tap of heater transformer secondary it, which is connected across heater element 8, and from said center tap to negative B battery terminal l5. 'Ihe anode it is connected to an external load circuit which, for purposes of illustration, is shown here as a condenser l8, connected across the primary of an iron cored transformer ll. From the other side of this load circuit, the anode lead proceeds to the positive "3 battery terminal l8. It will be understood that any suitable form of output circuit may be used in place of the one here shown, but, as illustrated, the secondary of transformer i7 is connected to further stages of amplification.

Referring to Fig. 2, the circuit is identical with that described in Fig. 1, except that variable condenser 30, having characteristics similar to in place of fixed condenser l3, which is omitted and variable condenser 5 is eliminated.

Fig. 3 is identical with Fig. 2, except that variable condenser 30 is removed from the circuit, thus placing biasing resistance Ii directly across the anode and cathode of the light-sensitive .cell 2, and an alternating E. M. F. from an external source i9 is impressed across all or part of biasing resistance I l by means of an adjustable contact 29.

Fig. 4 is identical with Fig. 3, except that a cathode resistor 2! is inserted in the circuit be-.

tween cathode l and all other connections to this cathode, and the alternating E. M. F. from external source I9 is applied across all or part of this cathode resistor 2| by means of adjustable contact 22.

Fig. 5 is identical with Fig. 3, except that an additional resistance 23 is inserted in series between the anode 3 of the light-sensitive cell and the biasing resistance II, and the alternating E. M. F. from external source I9 is applied through optional fixed condensers in each branch, 25 and 25, across all or part of this resistance 23 by means of adjustable contact 26.

Fig. 6 is identical with Fig. 3, except that the externally applied AJC. from source I9 is removed and, between the biasing resistance I! and the grid 9, iron cored coils 21 and 28 are connected in series with each other and with the circuit. Said coils are spaced in relation to each other and between them is inserted a rotating permanent magnet 29,- which may be replaced by a stationary iron core, energized from a separate A. C. source.

Fig. 7 is identical with Fig. 6, except that the iron cored coils 21 and 28 and the rotating or alternating member 29, described under the latter figure, are removed from the grid circuit and similar members 3!, 32, and 98 are connected, in the same mutual relation as before, in the plate circuit, between the output or load circuit and the positive B battery terminal 18.

Referring to Fig. 1,'the method of operation is as follows: When light from the source l is caused to strike the light-sensitive cell 2, a difference of potential is set up-across the anode 3 and the cathode 4, causing a current to fiow in resistor ii, if optional condenser I3 is omitted. If condenser i3 is inserted, a voltage will be impressed across it. This effect will, of course, be greatly magnified if the cell 2 is properly biased by a direct current potential from a suitable source. This E. M. F., through the medium of either arrangement will, in turn, be impressed upon the grid 9 of electron tube 6. Under these conditions, since no continuous variation is taking place in this impressed grid voltage, the output current from tube 6 will assume and maintain a steady value. The aforesaid potential which is impressed upon the entire circuit only when the cell 2 is illuminated, will also be impressed upon condenser 5, which we will assume happens to be set for a maximum capacity. This condenser will then take on a charge in accordance with or, ignoring the time factor, such a charge Q will be a function of the capacity C of condenser 5 and the potential E which is impressed as a result of illuminating the cell 2. Since the cell 2 has high inherent resistance, the potential of the'cell at the instant of illumination before current begins to flow in the external circuit will be a maximum. At this instant the voltage impressed across the condenser 5 will also be a maximum. Now, as 5 begins to assume a charge, and current begins to fiow in the external circuit of the cell, the current flowing through the cell will vary in accordance with its own IR drop and the back E. M. F. developed by condenser 5 and the rest of the circuit. Condenser 5 will continue to charge until the voltage across it equals the voltage impressed as a result of illuminating the cell 2. Therefore, during this transitory interval, the potential developed across 5 varies from zero to that of the impressed voltage.

If, prior to illuminating the cell, the condenser 5 is steadily rotated so as to vary continuously its capacity, the potential of the grid 9 will not be aifected,.but if the cell be illuminated While the capacity of 5 is thus continuously varying, the potential across and the charge upon 5 will be varied, and this variation will be transmitted to and impressed upon the grid 9 of the tube 6. This voltage impressed upon the grid will vary in synchronisni with the capacity variation of condenser 5. The voltage variation thus impressed upon the grid will cause a synchronous variation of the current flowing in the output or plate circuit of tube 6. If this plate current variation is at audio frequency, it may be amplified to any desired extent through conventional transformer type audio frequency amplifiers, one of which is indicated in the figure for purposes of illustration. No limitation, however, is implied as to the frequency range over which the grid voltage may be varied to produce the results described above.

In Fig. 2, the functions of the circuit are essentially the same as described in connection with Fig. 1. The only change here is that the condenser 30, which is similar to 5 and performs similarly in the circuit, is connected between the grid 9 and the light-sensitive cell 2, instead of across the cell.

In Fig. 3, an alternating'E. M..F. from an external source i9 is impressed upon the grid 9 in such a manner that, with the cell 5 darkened, the grid potential resulting from the combination of biasing potential I! and the alternating E. M. F. from source l9 will swing from such a neutral or negative value to such a further negative value that no current, or relatively little current, will flow in the output circuit of tube 6. When the cell 2 is illuminated, however, an additional D. C. potential of a steady value is impressed upon the grid 9. The alternating E. M. F. from I9 will, during one-half cycle, augment, and during the next half cycle, oppose this D. C. potential, with the result that during some part of each complete cycle of the source I9, the potential of grid 9 will swing sufficiently in a positive direction to permit a relatively large plate current to fiow in the output circuit of tube 6. Thus the cell operated D. C. voltage will control the average value of the total potential impressed upon the grid 9, and the grid potential will be varied at the frequency of the external source of alternating potential IS. The over-all result will be a pulsating component of plate current in the output circuit of tube 6. This pulsating current will fiow only when cell 2 is illuminated, and it will attain successive maxima at the frequency of the source l9. Such a current is easily amplified by any well known alternating current amplifying means.

The principle of operation of the circuit shown in Fig. 4 is the same asdescribed for Fig. 3. The

1 nating potential from external source I! is apand these oscillations will cease.

only difference between these two embodiments ,of the basic invention is that, in Fig. 4 the alterplied across an additional resistor connected directly in the cathode circuit of the tube 6, and this may require the use of a higher initial grid bias from biasing potential "in order to accom plish the same results as described forFlg. 3.

The circuit of Fig. 5 illustrates another modification of the'basic principle employed in Figs. 3

and 4. Here the alternating potential from exner described for Fig. 3, the grid of the tube is biased so that no current, or relatively little current, willflow in the plate circuit thereof when biasing potential i2 and external source l9 alone are acting. When the tube is illuminated, an additional D. C. potential is impressed upon the grid of the tube and this is successively opposed and augmented by the alternating potential from i9, so that during some part of each cycle of it, the combined potentials acting on the grid will cause it to swing sufficiently in a positive direction to permit a relatively large pulse of current to flow in the output circuit of the tube. The characteristics of this current are the same as described for Fig. 3.

The circuit shown in Fig. 5 possesses the ad ditional characteristic of beingable to function as a relaxation circuit. In this incarnation, the relaxation circuit proper comprises the source of biasing potential i2, biasing resistance ii, and the total impedance, as measured from grid to cathode, of the vacuum tube 6 and its associated output circuit. The characteristics of this relaxaing supplied from 69, relaxation oscillations will occur in the circuit l2, 6 l, and 8. Should the cell 2 now be illuminated, the additional D. 0. potential impressedthereby will upset the conditions of bias ln'the grid circuit of the tube which served to maintain the relaxation oscillations,

Thus, darkening and illuminating the cell 2 will control the starting and stopping of relaxation oscillations in the relaxation circuit described. The effect of these relaxation oscillations in the grid circuit of the tube will be to cause an otherwise direct plate current of a steady value to pulsate. Such a pulsating current may then be amplified by the usual type of transformer coupled amplifier, as shown.

The relaxation oscillations described may be caused to start instead of stop when the cell 2 is ,-illuminated, by merely changing the bias on the photocell, or on the tube. or on both, which methods are well known to the art.

The embodiment of the invention illustrated by the circuit of Fig. 6 operates as follows: When the cell 2 is dark and the iron cored coils 2i and 28 are being acted upon by a fluctuating magnetic field set up about the armature 29,'the grid 9 of the vacuum tube is so biased by means of i2 that no current, or relatively little current, will flow in the plate circuit of the tube. If the cell 2 is now illuminated, an additional D.-C. potential will be impressed on the grid 9. This will cause a current to flow through the coils 21 and 28, in-

ducing, a magnetic field which will interact with the magnetic field set up by armature 28. The result ofthis interaction will be to cause the potential of grid 8 to swing sufficiently in a positive direction during some part of the cycle of the fluctuating magnetic field about 29, to permit a relatively large component of plate current to flow in-the output circuit of the vacuum tube. This current will be pulsating in character and will pass through successive maxima at the frequency of the fluctuating magnetic field. Such a current may easily be amplified to any desired extent by conventional alternating current amplifying means, such as the transformer coupled E amplifier indicated in the figure.

In thecircuitof Fig. 7, the function of the various elements is the same as described for Fig. 6, the only difference in the two circuits being in the location of the armature and the iron cored coils. In thiscircuit, coils 3i and 32, and armature 88, which have similar characteristics -in all respects to elements 21, 28, and 29, de-

scribed in connection with Fig. 6, are included directly in the plate circuit of the vacuum tube, between the connection to the transformer pri-= mary and-the positive 13 battery terminal. In operation, the grid of the tube is biased so that no plate current, or relatively little plate current, will flow when the tube is darir. When the tube is illuminated, an additional D. 0. potential is applied to the grid of the tube, sufilcient to cause a continuous, relatively large plate current to flow in the output circuit of said tube. This current will fiow through the coils 8i and 82, setting up a magnetic field which will interact with the magnetic field set up about armature 3d. The result of this interaction will be a pulsating current in the plate circuit of the vacuurn tube, which will pass through successive maxima at the frequency of the fluctuating magnetic field set up about armature til, and which may be amplified to any desired extent by ordinary alternating current amplifying means.

The invention described herein may be menu iactured arid,used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. In an electrical circuit which includes a light-sensitive source of direct current potential, said source producing an uninterrupted direct current due to the incidence of substantially constant illumination upon the light-sensitive portion thereof, the method of imparting alternating characteristics to the output of said source which comprises cyclically varyingthe capacitive reactance of said circuit.

2. In an electrical circuit which includes a light-sensitive source of direct current potential, said source producing an uninterrupted direct current due to the incidence of substantially constant illumination upon the light-sensitive portion thereof, the method of amplifying the output of said source which comprises, imparting alternating characteristics thereto by cyclically varying the capacitive'reactance of said circuit,

of said source which comprises, imparting alternating characteristics thereto by cyclically varying the capacitive reactance of said circuit, applying the resultant energy to the grid of a thermionic tube to cause. a component of current to flow in the plate circuit of said tube durin part of each cycle of said reactance variation as aresult of the application of said energy tosaid put of said source which comprises, applying said" output to the grid of a thermionic tube to control the potential of said grid in accordance with said output and an alternating potentialof aysteady average value applied to said grid from a,source external to said circuit, causing a component of current to fiow in the plate circuit of said tube during part of each cycle of said alternating potential as a result of the application of said output to said grid, and amplifying by alternating current means the pulsating current thus produced in said plate circuit.

5. In an electrical circuit which includes a light-sensitive source of direct current potential, said source producing an uninterrupted direct current due to the incidence of substantially constant illumination upon the light-sensitive portion thereof, the method of imparting alternating characteristics to the output of said source which comprises, cyclically varying the inductive reactance ofsaid'circuit by electromagnetic interaction between a magnetic field set up by said output within said circuit and a fluctuating magnetic field set up outside said circuit. 1

6. In an electrical circuit which includes a light-sensitive source of direct current potential, said source producing an uninterrupted direct current due to the incidence of substantially constant illumination upon the light-sensitive portion thereof, the method of amplifying the output of said soure which comprises, imparting alternating characteristics thereto by cyclically varying the inductive reactance of said circuit by electromagnetic interaction between a magnetic field set up by said output within said circuit and a fluctuating magnetic field set up outside said circuit, and amplifying the resultant energy by alternating current amplifying means.

'7. In an electrical circuit which includes a light-sensitive source of direct current potential, said source producing an uninterrupted direct current due to the incidence of substantially constant illumination upon the light-sensitive portion thereof, the method of amplifying the output of said source which comprises, imparting alternating characteristics thereto by cyclically varying the inductive reactance of said circuit by electromagnetic interaction between a magnetic field set up by said output within said circuit and a fluctuating magnetic field set up outside said circuit, applying the resultant energy to the grid of athermionic tube to cause a component of current to flow in the plate circuit of said tube during part of each cycle of said fluctuating magnetic field as a result of the application of said energy to said grid, and amplifying by alternating current meansthe pulsating current thus produced in said plate circuit.

, capacity incircuit with'said source, a thermionic tube with appropriate power supply, grid leak,

and biasing potential, so connected that the output of said source, after being operated upon by said capacity, will be impressed upon the grid of said tube to cause variations in the potential of said grid, and an alternating current amplifying device in the output circuit of said tube,

whereby alternating characteristics are imparted to the direct current output from said source and said output may be amplified by said alternating current amplifying device.

9. In an electrical circuit which includes a light-sensitive source of uninterrupted direct current potential, said source producing said potential only when the light sensitive portion thereof is continuously illuminated, in combination, a thermionic tube with appropriate power supply, grid leak, and biasing potential, an alternating potential from an external source applied directly across a resistance in the input circuit of said tube so as to vary the potential of the grid thereof, said grid being so biased that no current, or relatively little current, will flow in the plate circuit of said tube while said alternating potential alone is acting upon said grid, means for applying the output of said source to raise the potential of said grid to the point where a component of current will flow inthe plate circuit of said tube' during part of each cycle of said alternating potential as a result of the application of said output to said grid, and an alternating current amplifying device in the output circuit of said tube, whereby the direct current from said source maybe amplified by said alter;

nating current amplifying device.

10. In an electrical circuit which includes a light-sensitive source of uninterrupted direct current potential, said source prodiicing said potential only when the light-sensitive portion thereof is continuously illuminated, in combination, a thermionic tube with'appropriate power supply, grid leak, and biasing potentiaL'm'eans within said circuit for setting up a magnetic field P with power from said source, means for applying.

a fluctuating magnetic field from an external source to interact with first said magnetic field, means for impressing the energy from said source after being operated upon by said fluctuating magnetic field upon the grid of said tube to cause variations in the potential of said grid with corresponding variations in the current flow in the output circuit of said tube, and an alternating current amplifying device in said output circuit, whereby the direct current output from said source may be amplified by said alternating current amplifying device.

11. In an electrical circuit which includes a light-sensitive source of uninterrupted direct current potential, said source producing said potential only when the light-sensitive portion thereof is continuously illuminated, in combination, a thermionic tube with appropriate power supply, grid leak, and biasing. potential, means within said circuit for setting up a magnetic field with power controlled by a current fiow from said source, means for applying a fluctuating magnetic field from an external source to interact with first said magnetic field to impart alternating characteristics to the energy flowing within said circuit, and an alternating current amplifying device in the output circuit of said tube, whereby the direct current output from said source may be amplified by said alternating ior the purpose of cyclically varying the potential impressed upon the grid thereof, whereby the output of said tube is given a character suitable ior further amplification by alternating current means.

13. In a circuit energized from a light-controlled direct current source oi relatively low potential, having an anode and a cathode branch, in combination, an electron tube having anode, cathode, and grid elements with conventional power supply, a source of grid biasing potential, a grid leak, an output circuit which includes the plate of said tube, and an electro-magnetic assembly, consisting of inductive elements within the field of a magnetic element of fluctuating polarity, in circuit with the enumerated combination for cyclically varying the output of said tube so as to give it a character suitable for further amplification by alternating current means. a

14. In a light-sensitive relaxation oscillator circuit, a thermionic tube having anode, cathode,

and grid elements with appropriate power supply, a source or biasing potential, resistance elements and capacity in the input circuit of said tube, said capacity being supplied in whole or in part by the inter-electrode capacities of said tube, an output circuit connected to the anode oi.

said tube, the circuit constants of the aforesaid combination being so assigned that a change in the bias on said grid may cause relaxation oscillatlons to commence and continue to flow in the input circuit of said tube, or, once flowing, to stop, depending upon the initial grid bias, and a light-sensitive source connected to impress a controlling direct current potential upon the grid of said tube when the light-sensitive element thereof is illuminated, whereby current variations in said output circuit will occur while relaxation oscillations are flowing in the input circuit of said tube, and said variations may be caused to start or stop by illuminating or darkening the light-sensitive element 01' said source.

15. In a light-sensitive relaxation oscillator circuit, a thermionic tube having anode, cathode, and grid elements with appropriate power sup ply, a source of biasing potential, resistance ele ments andcapacity in the input circuit of said tube, said capacity being supplied in whole or in part by the inter-electrode capacities of said tube, an output circuit connected to the anode oi said tube, the circuit constantsoi the aforesaid combination being so assigned that a change in the bias on said grid may cause relaxation oscillations to commence and continue to flow in the input circuit or said tube, or once flowing,

to stop, depending upon the initial grid bias, a

light-sensitive source connected to impress a controlling direct current potential upon the grid 01' said tube when the light-sensitive element thereof is illuminated, and alternating current amplifying means in said output circuit, whereby current variations in said output circuit will occur while relaxation oscillations are flowing in the input circuit of said tube, and said variations may be amplified by said amplifying means, or may be caused to start or stop by illuminating or darkening the light-sensitive element of said source.

ROBERT H. WORRALL. 

